Method and device for producing a three-dimensional object, and computer and data carrier useful therefor

ABSTRACT

The invention relates to a method for producing a three-dimensional object by solidification of a material solidifiable under the action of electromagnetic radiation by means of energy input via an imaging unit comprising a predetermined number of discrete imaging elements (pixels), The method comprises performing solidification with exposure using bitmap mask. The bitmap mask may be formed from a stack of bitmap data provided by an overlap analysis of a three-dimensional volume completely or partially enclosing a three-dimensional model of at least a part of the three-dimensional object to be produced. Alternatively, bitmap mask may be formed from a two-dimensional data set comprising overlap information. Solidification may be performing with exposure using bitmap mask generated “on the fly”. The invention is also directed to devices, and a computer and a data carrier useful for performing or executing the method.

TECHNICAL FIELD

The present invention relates to a method and a device for producing athree-dimensional object by solidification of a material solidifyableunder the action of electromagnetic radiation by means of energy inputvia an imaging unit comprising a predetermined number of discreteimaging elements (pixels). The present invention particularly relates todevices and methods in which a three-dimensional object is generatedbased on an exposure by means of a raster (bitmap) mask. Typically, thesmallest physical resolution in the mask is given by the size of apixel. A particular technique which may be applied to the imaging unitof the device is the Spatial Light Modulator (SLM) technology.

BACKGROUND ART

In the conventional field of stereolithography and rapid prototypingapparatus, three-dimensional objects are build by layer-wisesolidification of a material solidifyable under the action ofelectromagnetic radiation, commonly by photo-hardening of aphotopolymer. There are methods and devices for the layered-wiseconstruction of three-dimensional objects by exposure through an imagingunit comprising a predetermined number of discrete elements (pixels).Reference can be made, for example, to U.S. Pat. No. 5,247,180, U.S.Pat. No. 5,980,813, DE 93 19 405.5 U, DE 299 11 122 U, EP 1 250 995 A,EP 1 338 846 A, WO 01/00390, and WO 2005/110722.

With laser-based systems for photo-polymerisation, the energy or lightoutput in the exposure point is provided by energy setting of the laserbeam. To selectively harden a corresponding layer, the laser beam isscanned over the cross-sectional surface to be correspondingly hardened.The contours of the cross-sectional surface to be hardened can bescanned by the laser beam as a curve.

The layer-wise building of the three-dimensional object occurs bysolidification in a cross-sectional area corresponding to across-section of a three-dimensional (3D) model corresponding to thethree-dimensional object. Thus, the cross-sectional area to be hardenedlies in the XY building plane and respective layers are hardened to adesired layer thickness in the Z dimension (Z direction). For executionof this building method, a process includes a step of slicing 3D modeldata (STL) into a group of sliced two-dimensional (2D) data tocorrespond to the cross-sectional area to be exposed. This prior art isillustrated schematically in FIG. 1.

The afore-mentioned prior art transformation of 3D model data to sliced,layered 2D data corresponding to respective cross-sectional areas,however, is complex and involve extensive algorithms and computerprocessing. Furthermore, accuracy of a layer-wise hardening of aphoto-polymer depends on numerous factors, such as apportionment of thesliced cross-sections according to Z heights, setting of the contourlines of the sliced cross-sectional areas and a corresponding adjustmentof an energy (light output) source and respective control elements, etc.

OBJECT OF THE INVENTION

It is an object of the invention to improve method and device for theproduction of a three-dimensional object by providing a less complexsystem, involving relatively easy transformation of object informationinto appropriate building information. It is furthermore desirable tomake a relatively accurate building feasible at surface structures ofthe three-dimensional object to be produced.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodfor producing a three-dimensional object by solidification of a materialsolidifiable under the action of electromagnetic radiation by means ofenergy input via an imaging unit comprising a predetermined number ofdiscrete imaging elements (pixels), comprising the steps of:

a) providing a stack of bitmap data from a three-dimensional volumecompletely or partially enclosing a three-dimensional model of at leasta part of the three-dimensional object to be produced, wherein the stackof bitmap data had been generated by a process including:

superimposing a grid raster over the three-dimensional volume completelyor partially enclosing the three-dimensional model,

determining whether there is an overlap with the three-dimensional modelor not, setting bitmap data to an energy output status where an overlaphas been determined, or setting bitmap data to a status of no energyoutput where no overlap has been determined; and

b) performing solidification with exposure using bitmap mask formed fromthe stack of bitmap data provided in step a).

This first aspect of the invention is particularly suitable when theaforementioned bitmap stack has already been provided.

According to a second aspect of the invention, there is provided amethod for producing a three-dimensional object by solidification of amaterial solidifiable under the action of electromagnetic radiation bymeans of energy input via an imaging unit comprising a predeterminednumber of discrete imaging elements (pixels), comprising the steps of:

a) providing a two-dimensional data set from a three-dimensional volumecompletely or partially enclosing a three-dimensional model of at leasta part of the three-dimensional object to be produced, wherein thetwo-dimensional data set had been generated by a process including:

superimposing a grid raster over the three-dimensional volume completelyor partially enclosing the three-dimensional model,

determining whether there is an overlap with a three-dimensional modelor not,

transforming overlap information into transition information ofdifferent types including entry information as a first type, defined bytransition from the outside to the inside of a three-dimensional model,and exit information as a second type, defined by transition from theinside to the outside of a three-dimensional model,

saving the transition information in a two-dimensional data set; and

b) performing solidification with exposure using bitmap mask generatedusing the two-dimensional data set provided in step a).

This second aspect of the invention is particularly suitable when abitmap mask for solidification is generated by the aforementionedtwo-dimensional data set. It is possible to subsequently generate abitmap stack from the two-dimensional data set. Preferably, at least onebitmap is generated directly from the two-dimensional data set duringthe building process. Thus, it is feasible to control bitmap masks of animaging unit of a device for producing a three-dimensional object on thefly.

According to another aspect of the invention, there is provided a devicefor producing a three-dimensional object by solidification of a materialsolidifiable under the action of electromagnetic radiation by means ofenergy input via an imaging unit comprising a predetermined number ofdiscrete imaging elements (pixels), wherein the device comprises acomputer unit, an IC and/or a software implementation, respectivelyarranged to execute a stack of bitmap data transformed from athree-dimensional volume which includes at least a part of athree-dimensional model of the object to be produced, wherein eachbitmap data of the stack comprises information on an energy output levelsuch that pixels corresponding to a location within thethree-dimensional model are set to an energy output status, and pixelscorresponding to a location outside the three-dimensional model are setto a status of no energy output.

According to a further aspect of the present invention, there isprovided a device for producing a three-dimensional object bysolidification of a material solidifiable under the action ofelectromagnetic radiation by means of energy input via an imaging unitcomprising a predetermined number of discrete imaging elements (pixels),wherein the device comprises a computer unit, an IC and/or a softwareimplementation, respectively arranged to execute bitmap data transformedfrom a two-dimensional data set of transition information, wherein saidtransition information include entry information as a first type,defined by transition from the outside to the inside of athree-dimensional model, and exit information as a second type, definedby transition from the inside to the outside of a three-dimensionalmodel, said model corresponding to at least a part of thethree-dimensional object to be produced.

According to still another aspect of the present invention, there isprovided computer or a data carrier storing a bitmap data stack, whereineach bitmap data of the bitmap stack comprise information on energyoutput level for controlling an imaging unit which comprises apredetermined number of discrete imaging elements (pixels) correspondingto a rasterisation of a bitmap.

According to a still further aspect of the present invention, there isprovided computer or a data carrier a two-dimensional data setcomprising transition information which include entry information as afirst type, defined by transition from the outside to the inside of athree-dimensional model, and exit information as a second type, definedby transition from the inside to the outside of a three-dimensionalmodel, said model corresponding to at least a part of athree-dimensional object to be produced on the basis of the storedtwo-dimensional data set.

The computer or data carrier store a bitmap data stack or atwo-dimensional data set which respectively are particularly suitablefor executing a method according to the present invention in the firstor second aspect mentioned above, or for executing a device according tothe present invention mentioned above.

DESCRIPTION OF PRINCIPLES, FEATURES AND ADVANTAGES, AND OF PREFERREDEMBODIMENTS OF THE PRESENT INVENTION

The present invention is based on the building of a three-dimensionalobjects by means of mask exposure which obviates a mechanism of slicing3D model data. Thus, the present invention is a relatively simple systeminvolving less complex algorithm or computer processing or softwareimplementation. Further, although the amount of data can be reducedcompared to the conventional slicing technique, additional informationis made available, such that building parameters such as thickness ofthe layer to be solidified, fine exposure adjustment—especially atsurface structures of the three-dimensional object—, exposure times,etc. can be more roughly or more finely controlled where appropriate.According to the present invention, it is only necessary to determine,suitably by superimposing an appropriate grid raster or voxel gridraster over a three-dimensional volume, whether there is an overlapbetween a certain pixel location in bitmap data and thethree-dimensional model or not, and depending on the determinationresult, to set bitmap data and corresponding pixels to an energy outputstatus or not. Thus, a stack of bitmap data or a two-dimensional dataset respectively mentioned above can be formed, truly representing the3D model information. Moreover, depending on overlappingcharacteristics, surface structures of the three-dimensional object canbe accurately generated by appropriate bitmap control, which is mostsuitably carried out by allocating a grey value and/or a colour value topixels in bitmaps (which bitmaps are part of the whole stack of bitmaps)which are associated with the surface structures. The generation of abitmap data stack, or of a two-dimensional data set respectivelymentioned above (steps a) or a′) as indicated) can be executed simply bya virtual process, for example on a computer. Without intermediatelyforming a bitmap data stack, it is even possible to generate a bitmapmask on the fly during the 3D building process. The three-dimensionalobject can thus be efficiently and accurately produced in a relativelysimple and easy manner.

Particularly preferred advantages, features and embodiments are furtherdescribed in the following.

In comparison with the conventional layer data information based on theouter and inner contours within one cross section of the sliced data,according to the invention the three-dimensional model has not to besliced upfront to data generation, and the information is deriveddirectly from analyzing a model of the three-dimensional object.

The information may be stored in a 2½ dimensional format in that way,that each raster/grid point in XY contains the Z-information of allentrance and exit points of the Z-Vector at that XY point passingthrough the object.

This 2½ D information stored in a matrix, which may correspond to theresolution raster of the display device or bitmap, is not necessarilystored in form of a stack of bitmaps and is not necessarily directlyrelated to layers with a specific layer thickness. Layer thickness to besolidified may be varied depending on the data structure.

The 2½ D information file can be send to the machine, where the actuallyneeded layer information can be generated “on the fly” depending on theZ height/position of the layer.

Job files, possibly with different layer thicknesses and even withdynamic thickness adjustment, can be derived from the same file of 2½ Dinformation directly on the machine just by determining the layerthickness or ranges of different layer thicknesses (for dynamicadjustment). It is not necessary to slice the object into determinedlayers/cross sections to achieve the build information.

The data processing describes the build information of the whole buildenvelope, a bounding box of a three-dimensional model, or a volume ofarbitrary size including the 3D model completely or partly. Hence, thethree-dimensionally volume typically includes not only the 3D model.Different parts of a three-dimensional object can be produced togetheror separately depending on the adjustment of the build volume.

By calculating the three-dimensional intersection, or an approximationthereof, of a three-dimensional model and grid elements such as voxelelements, it is possible to adjust/control the light intensity at thatposition by allocating or assigning a grey value and/or colour value tothe pixel, which correlates to the grade of intersection.

In a preferred embodiment of the first and second aspects of theinvention, overlapping is determined in lines or areas respectivelyprojected from the grid raster through the three-dimensional volume.Alternatively, the grid raster is a voxel grid raster being superimposedover the three-dimensional volume, and overlapping is determined betweenvoxels of the voxel grid raster and the three-dimensional model. Thesemeasures provide efficient algorithms for determining and/or calculatingthe overlapping.

In a preferred embodiment of the first and second aspects of theinvention, the bitmap mask is generated from one or more bitmaps for XYplane, and when superimposing the grid raster over the three-dimensionalvolume, the grid raster is generated (i) from squares in the XY planerespectively corresponding to a sub-pixel, a pixel or multiple pixels ofthe bitmap, and (ii) from partitions in the Z direction perpendicular tothe XY plane. However, grid raster may be alternatively generated (i)from squares in the XY plane different from a raster of the bitmap.Further, the partitions in the Z direction perpendicular to the XY planemay be set independent from a layer thickness to be solidified in thelater building process. In further embodiment, which are made feasibleby the present invention, raster elements of the grid raster may haveeither the same size, or they may have varying sizes in the XY plane.

In the device according to the present invention, it is thereby possiblebut sufficient to set an energy output level of pixels depending on thedetermination, to lie within or outside of the three-dimensional modelor to lie between points corresponding to entry information and exitinformation respectively, by an overlap between a three-dimensionalvolume completely or partially enclosing the three-dimensional model anda grid raster projection superimposing the three-dimensional model. In apreferred embodiment of the device, it is likewise efficient that anenergy output level of pixels is determined by an overlap between thethree-dimensional model and lines or areas respectively projected from agrid raster through the three-dimensional volume which includes thethree-dimensional model. It is likewise efficient for the device that,alternatively, an energy output level of pixels is determined by anoverlap between the three-dimensional model and a voxel grid rastersuperimposing the three-dimensional volume which includes thethree-dimensional model.

These different possibilities renders the system of the presentinvention very flexible to demands and desires of producing thethree-dimensional object, especially depending on necessities anddesires of providing fine or rough structures. For example, for volumeparts where no information or only few information is obtained from theoverlap analysis, rough rasterisation can be applied to the bitmap mask,whereas for volume parts where a lot of information or detailedinformation is obtained from the overlap analysis, fine rasterisationcan be applied to the bitmap mask. Thus rough and fine rasterisation canbe combined where appropriate. This also reduces the amount of data tobe saved, stored or processed during the whole production method.

In a preferred embodiment of the first and second aspects of theinvention, the stack of bitmap data (either provided in step a) orgenerated from the two-dimensional data set from step a′)) includes astack of multiple bitmaps for XY plane, and raster points of bitmapsrepresenting pixels in the Z direction are set to an energy outputstatus in the region between an entrance point or entrance area and anexit point of a line or area respectively projected from thecorresponding grid raster in the Z dimension through thethree-dimensional model. The provision or generation of stack of bitmapdata in this manner significantly reduces the amount of data to besaved, stored and/or processed.

In a further preferred embodiment, the saved data on transitioninformation in the two-dimensional data set are sent to a device forproducing the three-dimensional object comprising the imaging unit, andwhen performing solidification in step b), one or more bitmap masks is(are) generated “on the fly” using the transition information providedin step a). By this measure, the actually needed layer information canbe generated directly from the two-dimensional data set during thebuilding process (i.e. on the fly) depending on the actual Z height or Zposition of the layer.

In a preferred embodiment of the first aspect of the invention, thebitmap stack provided in step a) comprises only bitmaps which differfrom each other. Similarly, in a preferred embodiment of the secondaspect of the invention, the two-dimensional data set provided in stepa′) is used to generate a bitmap stack, or to directly generate bitmapmasks, which bitmap stack or bitmap masks comprises only bitmaps whichdiffer from each other. By this measure, the information finally used inthe building process is reduced to the information actually needed inthe solidification of layers. In particular, multiple layers requiringthe same building conditions, especially on the circumferentialstructure and/or the thickness, may be solidified by commonly using asame bitmap mask, whereas other layers requiring different buildingconditions, especially on the circumferential structure and/or thethickness, may be solidified by using the different bitmap masks,respectively. Further, the same bitmap may be used for more than onelayer to be solidified. Alternatively or in combination, the same bitmapmay be used multiple times for an individual layer.

In a preferred embodiment of the first and second aspects of theinvention, when superimposing a grid raster over the three-dimensionalvolume, each grid raster unit comprises multiple projected lines, and agrey value and/or a color value is allocated to a corresponding rasterelement representing a sub-pixel, a pixel or multiple pixels of a bitmapwhen the determined overlappings in the respective projected linesdiffer from each other. Alternatively, determining whether there is anoverlap includes a determination of a degree of overlap, and as a resultthereof, pixels in a generated bitmap mask are specifically set to aratio of energy output depending on the degree of overlap. In a furtherpreferred embodiment, the degree of overlap is determined between voxelsof a voxel grid raster and a three-dimensional model, and pixels in agenerated bitmap mask are set to a gray value and/or a color value whenthe degree of overlap is below 100% and above 0%. Accordingly, in thedevice according to the present invention the imaging unit iscontrollable by adjusting and/or controlling the energy output level viaa specific gray value and/or color value. These measures allow forobtaining more or less detailed information about certain structuressuch as surface structures, and thus for a fine adjustment of buildingparameters.

In a preferred embodiment of the first and second aspects of theinvention, a thickness of layers formed by solidifying the solidifiablematerial is controlled to obtain same and/or different thicknesses,depending on the data structure of bitmap data provided in the stack ofbitmap data, or depending on the data structure in the two-dimensionaldata set. As a further possibility made feasible by the invention, thethickness may be the same in certain Z dimensional ranges, but may bedifferent in other Z dimensional ranges as needed or desired. Varyingthickness control further expands the flexibility of the systemaccording to the present invention.

In the device according to the invention, a raster of the imaging unitcomprises a predetermined number of discrete imaging elements (pixels)arranged as a dot, a line or as a matrix, wherein the imaging unitcomposes a layer image pixel-specific from the bitmap data. This enablesa precise solidification of the solidifyable material depending on theprovided information data.

The computer or the data carrier according to the present invention arevaluable products which are respectively effective for controllingbitmap masks of an imaging unit of a device for producing athree-dimensional object In a preferred embodiment of the computer orthe data carrier according to the present invention, the information onenergy output level is determined by an overlap as described above. Inparticular, the two-dimensional data set may be arranged to generate abitmap stack, or it may be arranged to generate at least one bitmap ofon the fly without generating an intermediate bitmap stack. It isparticularly advantageous that bitmap masks, which are provided by abitmap stack in a computer or a data carrier or which is generated fromthe two-dimensional data set, comprise only bitmaps which differ fromeach other.

The bitmap data stack, or the two-dimensional data set may be saved orstored in a job file together with information on building parameters.In a particular aspect of the present invention, a two-dimensional dataset is saved or stored in a computer or a data carrier as an informationin a quasi 2½ dimensional format, comprising: information on an XY pointof a raster grid superimposed over a three-dimensional volume completelyor partially including the three-dimensional model; and entryinformation and exit information as a quasi Z dimensional informationfor respective raster grid elements in XY. A rasterization in the Zdirection can thus be omitted. Further, such two-dimensional data set iseffective and sufficient for generating a building data package incombination with corresponding exposure curves. Further, each bitmapmask may be used with varying exposure times to produce correspondinglyvariable hardening depths.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically and illustratively shows a scheme demonstratingconventional transformation from three-dimensional object data intosliced, two-dimensional (cross-sectional) data in a prior art method forproducing a three-dimensional object.

FIG. 2 schematically and illustratively shows a scheme demonstratingtransformation of three-dimensional object data into two-dimensionalbitmap data in accordance with an embodiment of the present invention.

FIG. 3 schematically shows an embodiment of the invention how a gridraster may superimpose over a 3D volume enclosing a three-dimensionalobject to be produced, which is exemplified by a form of a sphere.

FIG. 4A shows an embodiment according to the present invention,exemplifying an approach to determine an overlap or lack of overlapalong lines projected from a grid raster superimposed as shown in FIG.3.

FIG. 4B schematically shows another embodiment, exemplifying anotherapproach to determine an overlap or lack of overlap along linesprojected from sub-raster points of a grid raster superimposed as shownin FIG. 3.

FIG. 4C schematically shows another embodiment of the present invention,exemplifying still another approach to determine whether there is anoverlap or lack of overlap of areas protected from a grid raster assuperimposed as shown in FIG. 3.

FIG. 5 shows another embodiment of the invention involving a process ofsuperimposing a voxel grid raster over a 3D volume.

FIGS. 6A to 6F schematically show steps in a process for transformingvoxel grid raster information into a stack of bitmaps in accordance withanother embodiment of the present invention.

FIG. 7A to 7C schematically show steps in a process for determiningvoxel grid overlappings and bitmap data settings in accordance with anembodiment of the present invention.

FIG. 8A schematically illustrates a data carrier and/or a computerstoring a bitmap data stack and additional parameters useful inaccordance with an embodiment of the present invention.

FIG. 8B schematically illustrates a data carrier and/or a computerstoring a data set of transition information and additional parameteruseful in accordance with an embodiment of the present invention.

FIG. 9 schematically shows an example of a device for producing athree-dimensional object, to which the method and the system accordingto the present invention can be applied.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

In the following, principles, objects, preferred features and advantagesof the present invention are described in more detail by referring topreferred embodiments of the present invention in connection with theaccompanying drawings, noting however that the description isillustrative only and by no means limits the present invention.

A scheme for schematically illustrating a basic principle of the presentinvention is shown in FIG. 2. The basis concept resides in that for eachpixel of a bitmap mask used for the exposure of a layer of thethree-dimensional volume enclosing the three-dimensional object to besolidified, it must be determined and decided only whether it lieswithin or outside of a 3D model of the three-dimensional object. Asfurther shown in FIG. 2, determination of overlappings and pixelsettings are carried out for all bitmap layers of a bitmap stack. Thus,by any one of possible embodiments used for transforming 3D model datainto bitmap data, a stack of bitmap data can be formed to generaterespective bitmap masks for the exposure of solidifiable material. Eachbitmap data and correspondingly bitmap mask may be used to expose one orseveral layers of a three-dimensional object to be produced. Accordingto the present invention, a mechanism for slicing 3D data to generatelayered 2D data for cross-sectional areas is obsolete, and there is norequirement of calculating sectional contours as in the prior art shownschematically in FIG. 1.

FIG. 3 schematically shows an embodiment according to the presentinvention, wherein a grid raster is superimposed over athree-dimensional volume which encloses, at least partially, athree-dimensional model of a three-dimensional object to be produced.Here, for a 3D model shown in the form of a sphere 100, a grid raster200 is imposed virtually over the three-dimensional volume. Based onthis grid rasterisation, it is determined whether, in respective unitareas of the grid raster projected from the grid rasterisation 200,there is an overlap with the 3D model or not. This is respectivelydemonstrated in FIG. 3 for an n-th grid raster unit 200 ^(n) for thecase of an overlap, and for a grid raster unit 200′ when there is a lackof overlap.

Possible approaches how to determine an overlap between the grid rasterand the 3D model will be described in the following with respect toFIGS. 4A, 4B and 4C respectively. Same elements are denoted by samereference signs.

According to the embodiment shown in FIG. 4A, lines are virtuallyprojected from each centre of respective grid raster unit(representatively shown by line 250 for the n-th grid raster unit 200^(n) of FIG. 3). Placing the grid raster into the XY plane (whichcorresponds to an XY building plane for building layers in correspondingXY planes of the three-dimensional object to be produced), the line 250is projected parallel to the Z-axis (i.e. along the Z dimension), and itis determined at which Z points/heights of the Z-axis (or Z dimension)the projected line 250 enters the 3D model, and at which point or heightof the Z-axis (or Z dimension) the protected line 250 exits the 3D model(indicated by circular points in FIG. 4A). For setting bitmap data,which may be provided in advance or which may be advantageouslygenerated “on the fly” when needed at the build process, it isdetermined for each grid raster unit corresponding to a respectiveraster unit of the bitmap, whether or not the Z value is between anentering point and an exit point: if this is the case (for example ingrid raster unit 200 ^(n) between the entrance and exit points shown inFIG. 4A), all corresponding pixels of bitmap data in the Z dimension areset to an energy output status (for example, for outputting whitelight); if this is not the case (for example as shown for grid rasterunit 200′ in FIG. 3, or for such bitmap data lying below the entrancepoint or above the exit point in the grid raster unit 200 ^(n) shown inFIG. 4A), corresponding pixels of bitmap data in the Z dimension are setto a status of no energy output (for example blocking light output; orblack colour value). From the bitmap data thus generated, comprising astack of XY bitmap data like the one illustrated in FIG. 2 andcontaining the information on the energy output status (i.e. energyoutput or white light status; or energy blocking or black light status)obtained from the aforementioned overlapping analysis, an imaging unitof a 3D-object producing device can be controlled to form exposure maskscorresponding to respective bitmap layers. Accordingly, pixels of anexposure mask of the imaging unit of the 3D-object producing device, bymeans of a computer unit such as a CPU, an IC and/or a softwareimplementation, are correspondingly set, pixel-specifically, to an ON orOFF state, respectively, based on the corresponding bitmap data. Athree-dimensional object, e.g. represented by the spherical 3D model100, is thus physically produced by layered-wise exposure correspondingto respective bitmap data in a highly effective and easy manner.

FIG. 4B shows a preferred embodiment of the present invention, by whichsurface structures of a three-dimensional object, corresponding tosurfaces of a 3D model, can be produced more accurately by means of greyvalue and/or colour value control. In order to obtain information onsurface structures, the following approach may be adopted. Instead ofone line projecting from an individual grid raster unit, multiple lines,e.g. four lines 250 ¹, 250 ², 250 ³ and 250 ⁴, are projected from anindividual grid raster unit. In an embodiment shown in FIG. 4B, theselines are projected from respective centers of sub-raster elementscomposing a grid raster unit 200 ^(n). Projection is made, in a virtualprocess, parallel to the Z axis, and it is determined again at whichpoint or height the Z axis the projected lines enter into the 3D modeland at which point or height of Z axis the lines exit the 3D model. Forallocating a grey value and/or a colour value from a grid raster unit toa corresponding pixel of the bitmap and thus of the exposure mask, it isdetermined which sub-elements of a grid raster unit in the Z dimensioncomprise locations between an entrance and an exit point. From the sumof the sub-raster elements where this is the case, a corresponding greyvalue and/or colour value is associated with the grid raster unit andthereby allocated to the corresponding pixel in the bitmap data. Forexample, if the determined overlappings in the respective projectedlines drawn from the centers of sub-units of a grid raster unit differfrom each other, a grey value and/or a colour value is allocated to thecorresponding pixel of the bitmap in the bitmap data.

Pixels in bitmap layers between entry and exit point are set to energyoutput status, and pixels in bitmap layers below the entry point andabove the exit point are set to status of no energy output. In apreferred embodiment, the level of grey value and/or colour value isdetermined and set in the corresponding bitmap data based on a deviationof the overlappings of the multiple projected lines (i.e. of 250 ¹, 250², 250 ³ and 250 ⁴) from the mean value of these overlappings per rastergrid unit (i.e. 200 ^(n)). For example, the lower the deviation per gridraster unit, the lower the level of grey value or colour value may beset. This manner of determination and setting may be suitably applied tothe surface portions of the upper and/or lower hemisphere of thespherical form shown in FIG. 4B.

In other surface portions, for example an equatorial section of thespherical form shown FIG. 4B, there may be grid raster units whosesub-units partly do have an overlap, whereas a remaining part thereofwill not have an overlap with the three-dimensional model (not shown).In this case, the degree of grey value and/or colour value can bedetermined depending on the ratio of those multiple projected lines pergrid raster unit which do have an overlap, relative to those which donot have an overlap with the three-dimensional model. Partialoverlappings in sub-raster elements may thus be determined andsubsequently used for setting bitmap data for providing additionaluseful information for grey value and/or colour value control.

In this embodiment, it will become apparent that the determination andsetting for bitmap data of surface structures will have a tendencytowards higher accuracy with an increasing number of sub-rasterisationof grid raster units, and correspondingly with an increasing number ofvirtual lines projected form individual grid raster units. Accuracy thesurface structures may thus be adjusted according to a desire or demandfor a corresponding three-dimensional object.

Another approach is shown in FIG. 4C. In this embodiment, an area isprojected in a virtual process from a grid raster unit, such as a squarebeing projected in a column-like form to be superimposed with thethree-dimensional model, as shown in FIG. 4C for the 200 ^(n) gridraster unit. As described above, it is likewise determined whether thereis an overlap with the 3D model, as shown in FIG. 4C in the range of Zbetween the two lower and upper cross-sectional areas denoted byreference signs 300A and 300B, respectively, and corresponding areas inthe bitmaps of the bitmap data are set to the energy output status (e.g.for white light exposure). If the Z point or height is located in thecross-sectional area region 300A or 300B, the actual overlapping area iscalculated and, depending on the result of this calculation, acorresponding grey value and/or colour value is set and allocated to thecorresponding part of the bitmap in the bitmap data.

An area representing a grid raster unit (e.g. 200 ^(n)) may correspondto one pixel, to a part of a pixel, or to a group of multiple pixels inthe bitmap and thus in the bitmap mask.

Another embodiment for providing a bitmap data from a 3D model inaccordance with the present invention based on a so called direct voxelrasterisation of a 3D model is schematically shown in FIGS. 5 and 6A to6F. First, as shown in FIG. 5 (partly in the upper row andcomprehensively in the lower row), a matrix is defined by a virtualvoxel grid. Thereby, a voxel grid raster is generated from squares in XYplane to correspond to a pixel rastering of a bitmap in the bitmap datastack and thus to correspond to a pixel rastering of an exposure maskfor an exposure by an imaging unit of 3D-object producing device. Here,the square size in the XY dimensions of the voxel grid rastercorresponds to the size of a pixel in the bitmap. It may insteadcorrespond to a multitude or a fraction of the size of a pixel in thebitmap (corresponding to respective bitmap masks of the imaging unit ofthe 3D-object producing device). in a virtual process the voxel gridshown in FIG. 5 is superimposed over a three-dimensional volumeenclosing a 3D model, and subsequently overlappings are determined andbitmap data are set to generate bitmap data stack (generated in aadvance or on the fly as mentioned above).

To illustrate the process the order of FIGS. 6A to 6F schematically showhow this can be executed. The drawings on the left side illustrate thisprinciple three-dimensionally in XYZ, whereas the drawings on the rightside show a 2D-illustration in an XZ plane, respectively.

As shown in FIG. 6A, a build envelope corresponding to a projected areaof the imaging unit of the 3D object-producing device is formed. Asspecifically shown in the left and right illustrations of FIG. 6A, asphere of 3D model data can be placed over the build envelope. Asfurther shown in FIG. 6B, the projected picture in the XY planecorresponds to a bitmap image composing a matrix of squared pictureelements (pixels).

For each voxel grid unit corresponding to a pixel element of the bitmapand thus of the bitmap mask for exposure, a line is projected from thecenter in the Z direction, as shown in FIG. 6C.

Then, as shown in FIG. 6D, an estimation is carried out of theintersection points of every projected line with this sphere model (inthe left 3D illustration), or with the circle (in the right 2Dillustration). There are two different types of intersection points: Ina first type, the protected line is going into the 3D model: thisintersection is defined as entry point. In a second type, the projectedline leaves the 3D model: in this case, the intersection is defined asexit point. In the 2D illustration of FIG. 6D, the entry points ofrespective projected lines are shown by crossing symbols, whereas exitpoints of the projected lines are shown by square symbols.

Next, the set of estimated intersections is used to approximate theamount of overlapping of model volume or model area within a voxel gridelement (voxel raster unit). Now, there is no longer a relationship tothe original 3D model. This is illustrated in FIG. 6E by overlappinglines between entry points and exit points of the voxel grid raster.Saving entry and exit points of each raster element, if such entry andexits points occur, produces a data package comprising a rasteredrepresentation of the 3D volume and thus of a 3D model included therein.This rastered representation can then be used to build a complete bitmapstack in advance to be subsequently sent to a 3D object-producingdevice, or can be sent directly to the 3D object-producing device togenerate appropriate bitmap masks during the building process (on thefly).

As shown in FIG. 6F, every voxel or volume pixel range that lies betweenan entry point and an exit point of its correspondingly projected lineis set to a status of full overlapping with the 3D model and thus is setin the bitmap data to an energy output status (for example, light outputor white colour). All other voxels or volume pixel ranges are set to acomplete lack of overlapping by the 3D model and thus is set in thebitmap data to a status with no energy output (light output blocking orblack colour). The information in a voxel plane, i.e. in the XY planecorresponding to a voxel element, is used to generate a bitmap mask. Thebitmap mask for exposure contains black pixels for areas which should benot cured and white pixels for areas where the photopolymer should becured.

For those layers to be solidified with no difference in the outerdimensions, the same bitmap mask can be used several-fold. Thus, thereis no necessity of generating a new bitmap mask for every new layer tobe hardened.

With the system according to this embodiment described above, a3D-object producing device uses a mask projection system which iscapable of projecting millions of squared light spots arranged in amatrix, the matrix being composed of corresponding voxel elementsdescribed above.

In the following, other embodiments of the present invention will bedescribed by reference to FIGS. 7A to 7C. First, as shown in the leftpart of FIG. 7A, a voxel grid raster is superimposed over a 3D volumeenclosing a 3D model (shown here again in the form of a sphere). Next,as shown by the transformation from the left side to the right side ofFIG. 7A, it is determined whether there is an overlap between respectivevoxel elements of the voxel grid raster with the 3D model or not.Depending on the result of the determination, bitmap data correspondingto respective voxel elements are set to a status of energy output ornot.

According to a preferred embodiment, colour coding by suitable greyvalues and/or colour values depending on the size of the overlap, i.e.the size of the intersection area/volume, is carried out as shown inFIG. 7B. Specifically, as shown in the illustration on the left side ofFIG. 7B, a colour code is set to “black” if there is no intersectionarea/volume overlap, a grey value of approximately intermediate level isset for an intersection area/volume of about 40%, and a colour code“white” is set for an intersection area/volume of 100% in respectivelyrastered voxel elements. The colour codings of overlapping intersectionareas/volumes between a voxel matrix and a 3D model is generated for thewhole build volume rastered by the voxel grid raster, as shown in themiddle illustration of FIG. 7B, and is then further transformed into thebitmap data settings of corresponding XY voxel planes of bitmap data, asindicated in the right-side illustration of FIG. 7B. For thisprocessing, FIG. 7C specifically shows the conversion of colour codingsof the overlapping intersection areas/volumes between every voxelelement and the 3D model (see left illustration in FIG. 7C) intopixel-specific intensity values (comprising black, white and greyvalues), depending on the result of the overlapping determination (seemiddle illustration of FIG. 7C). At the end (see right illustration inFIG. 7C), the build volume is rastered into a stack of bitmaps beingcomposed of respective bitmap data. Based on the generated bitmap stack,an imaging unit of a 3D-object producing device is controlled, whereinevery bitmap mask for one or more corresponding layer(s) to besolidified contains energy output intensity values, including areas ofblack pixels which should not be cured, areas of white pixels where aphotopolymer should be fully cured, and a areas of grey pixels with areduced level of curing. With this embodiment, a three-dimensionalobject can be efficiently produced with high accuracy even in surfacestructures. Further, as becomes apparent from FIG. 7C, respectively twobitmaps of the bitmap stack resemble each other, namely the bottom andtop bitmaps representing only black pixels, and both middle bitmapsrepresenting black and grey pixels. For such an exemplified situationthe whole bitmap stack could be reduced to a half of the bitmaps (e.g.the first and second ones from the bottom) while keeping the wholeinformation for all layers to be solidified, hence reducing the amountof data to be saved, stored and/or to be processed.

In the above description, principles and embodiments of the inventionhave been specifically exemplified. However, it will be come apparent toa person skilled in the art that various variations and modificationsare possible. Of course, any desired shape of the 3D model andcorrespondingly the three-dimensional object can be produced. Also, onlya portion of a three-dimensional object may be produced by the presentinvention. Furthermore, the principle of the invention as described andembodied above may be applied to more complex 3D structures. Forexample, there may be a multitude of overlapping portions interrupted inthe Z dimension of a 3D model with lines or areas projected from a gridraster, or with voxel elements of the voxel grid raster, while stillapplying the principles of the present invention. Furthermore, the stepsof providing bitmap data on the one hand and of performingsolidification of a material on the other hand may be carried outinter-actively or simultaneously, or may be carried out separately intime and/or location, or any combination thereof. In one embodiment, thebitmap data (in the form of a bitmap stack or of a two-dimensional dataset as described above) can be provided at a location remote from thelocation where the actual solidification performing process is carriedout.

Valuable technical products for assisting in the performance of themethod and for executing the device of the present invention, such as acomputer or a data carrier respectively storing a bitmap data stack or atwo-dimensional data set as described above, are also provided by thepresent invention.

FIGS. 8A and 8B schematically illustrate embodiments of a computer or adata carrier of the present invention. Accordingly, a stack of bitmapscorresponding to a build volume of a three-dimensional object to beproduced comprises, for layers to be solidified, information data on anenergy output level adapted for controlling an imaging unit whichcomprises a number of pixels suitably but not necessarily correspondingto the rasterisation of the bitmap. This bitmap stack is combined withcorresponding build parameters for every bitmap mask, to thereby createa job file. Build parameters may include, but are not limited toselected layer thickness of respective layers to be solidified forbuilding a three-dimensional object, exposure times per bitmap mask,number of exposures per layer be solidified, information on selectedlight source and optionally on selected wavelengths, etc. The thuscreated job file can be stored on a data carrier such as a disk. It maybe transferred to, or is alternatively directly stored in a computer.The computer may further comprise a CPU and software implementation forexecuting the job file as illustrated in FIGS. 8A and 8B. The job filecan be executed for controlling an imaging unit of a 3D-object producingdevice either directly with appropriate signal linings therebetween, oronline or in a remote manner via suitable signal transfer, or acombination thereof. As exemplified in FIG. 8B and similar to the abovedescription in connection with FIG. 7C, before data are saved/stored ona data carrier and/or a computer, a whole stack of bitmap data isreduced to a minimum number of bitmaps necessary for constructing thethree-dimensional object or a part thereof, hence reducing the amount ofdata to be saved, stored and/or to be processed.

An illustrative embodiment of a possible 3D-object producing device isshown for illustrative purposes in FIG. 9. The device for layer-wiseproducing a three-dimensional object 3 by layered hardening of aphoto-hardening material 4 includes mask projection 8, wherein theprojection unit 1 with imaging optics 2 is provided above basin 6,filled with photo-hardening material 4. The object 3 is hardened inlayers on a carrier plate 5 which can be moved in vertical directionwithin the basin 6.

With a method based on photo-polymerization, the light radiationnecessary for hardening is projected into the processing level. Exposureis effected for example by means of a multimedia projector. The image iscomposed by individual image points (pixels) of a bitmap. The bitmapmask can be formed by a Spatial Light Modulator with the pixels beingarranged in a mutually spatially fixed manner in the plane. A currentlystandard, exemplary resolution for such semiconductor elements isSXGA+1400×1050 pixels.

The imaging unit which can be used for being controlled in accordingwith the present invention may not only be a multimedia projector, butfurther includes, for example, a LC display (reflexive or transmissive),a LED or laser diode line (which is moved over the layer orthogonally tothe line), a light valve technology apparatus (M EMS technology), or thelike.

Furthermore, the level of energy output status, such as light outputlevel for the exposure of a bitmap mask, can be adjusted by means whichare known. For example, the levels may comprise:

a1) ON and OFF states, by an essentially complete energy transmission(white) or, respectively, by an essentially complete energy blockingwithout energy transmission (black), in transmissive systems (especiallywith light valves); ora2) ON and OFF states, by an essentially complete energy reflection intothe optical axis (white in the projection image) or, respectively, by anessentially complete reflection out of the optical axis into an opticalabsorber (black in the projection image), in reflexive systems (inparticular in a Digital Micromirror Device [DMD] or a Liquid Crystal onSilicon [LCOS] for digital light processing [DLP]); and additionallyb1) a predetermined, desired number of gray levels, orb2) a predetermined, desired number of color values. The color valuescan represent a color tone and/or a color density or, respectively,intensity.

Although, the present invention has been described in detail above byreferring to specific embodiments and illustrative drawings, the presentinvention is by no way limited thereto. Rather, it becomes apparent thatvarious variations and modifications are possible, and the presentinvention is defined only by the spirit and scope of claims attachedherewith.

1-40. (canceled)
 41. A method for producing a three-dimensional objectby solidification of a material solidifiable under the action ofelectromagnetic radiation by means of energy input via an imaging unitcomprising a predetermined number of discrete imaging elements (pixels),comprising the steps of: a) providing a two-dimensional data set from athree-dimensional volume completely or partially enclosing athree-dimensional model of at least a part of the three-dimensionalobject to be produced, wherein the two-dimensional data set had beengenerated by a process including: superimposing a grid raster over thethree-dimensional volume completely or partially enclosing thethree-dimensional model, determining whether there is an overlap with athree-dimensional model or not, transforming overlap information intotransition information of different types including entry information asa first type, defined by transition from the outside to the inside of athree-dimensional model, and exit information as a second type, definedby transition from the inside to the outside of a three-dimensionalmodel, saving the transition information in a two-dimensional data set;and b) performing solidification with exposure using bitmap maskgenerated using the two-dimensional data set provided in step a). 42.The method according to claim 41, wherein saved data on transitioninformation in the two-dimensional data set are sent to a device forproducing the three-dimensional object comprising the imaging unit, andwhen performing solidification in step b), one or more bitmap masks is(are) generated “on the fly” using the transition information providedin step a).
 43. The method according to claim 41, wherein thetwo-dimensional data set provided in step a′) is used to generate abitmap stack, or to directly generate bitmap masks, which bitmap stackor bitmap masks comprises only bitmaps which differ from each other. 44.The method according to claim 41, wherein a thickness of layers formedby solidifying the solidifiable material is controlled to obtain sameand/or different thicknesses, depending on the data structure in thetwo-dimensional data set.
 45. A device for producing a three-dimensionalobject by solidification of a material solidifiable under the action ofelectromagnetic radiation by means of energy input via an imaging unitcomprising a predetermined number of discrete imaging elements (pixels),wherein the device comprises a computer unit, an IC and/or a softwareimplementation, respectively arranged to execute bitmap data transformedfrom a two-dimensional data set of transition information, wherein saidtransition information include entry information as a first type,defined by transition from the outside to the inside of athree-dimensional model, and exit information as a second type, definedby transition from the inside to the outside of a three-dimensionalmodel, said model corresponding to at least a part of thethree-dimensional object to be produced.
 46. A computer storing atwo-dimensional data set comprising transition information which includeentry information as a first type, defined by transition from theoutside to the inside of a three-dimensional model, and exit informationas a second type, defined by transition from the inside to the outsideof a three-dimensional model, said model corresponding to at least apart of a three-dimensional object to be produced on the basis of thestored two-dimensional data set.
 47. The computer according to claim 46,wherein the two-dimensional data set stores information in a quasi 2½dimensional format, comprising: information on an XY point of a rastergrid superimposed over a three-dimensional volume completely orpartially including the three-dimensional model; and entry informationand exit information as a quasi Z dimensional information for respectiveraster grid elements in XY.
 48. The computer according to claim 46,wherein the two-dimensional data set is arranged to generate a bitmapstack, or is arranged to generate at least one bitmap of on the fly, forrespectively controlling bitmap masks of an imaging unit of a device forproducing a three-dimensional object.
 49. The computer according toclaim 48, wherein the generated bitmap stack, or the directly generatedbitmap masks comprise only bitmaps which differ from each other.
 50. Adata carrier storing a two-dimensional data set comprising transitioninformation which include entry information as a first type, defined bytransition from the outside to the inside of a three-dimensional model,and exit information as a second type, defined by transition from theinside to the outside of a three-dimensional model, said modelcorresponding to at least a part of a three-dimensional object to beproduced on the basis of the stored two-dimensional data set.
 51. Thedata carrier according to claim 50, wherein the two-dimensional data setstores information in a quasi 2½ dimensional format, comprising:information on an XY point of a raster grid superimposed over athree-dimensional volume completely or partially including thethree-dimensional model; and entry information and exit information as aquasi Z dimensional information for respective raster grid elements inXY.
 52. The data carrier according to claim 50, wherein thetwo-dimensional data set is arranged to generate a bitmap stack, or isarranged to generate at least one bitmap on the fly, for respectivelycontrolling bitmap masks of an imaging unit of a device for producing athree-dimensional object.
 53. The data carrier according to claim 50,wherein the generated bitmap stack, or the directly generated bitmapmasks comprise only bitmaps which differ from each other.